This invention relates to a punching and stamping tool for joining together overlapping steel bands. In particular, the present invention relates to a punching and stamping tool used in a fastening device to fasten together the overlapping ends of a strap wrapped around a package.
Hooper and strapper devices for binding together the overlapping ends of a metal strap wrapped around a package generally comprise an upper tool having a die which moves onto a corresponding stationary lower tool having a punch. The upper and lower tools act on overlapping ends of the strap to execute a punching and stamping operation to produce at least a pair of angled hooking cuts in both of the overlapping ends as disclosed, for example, in U.S. Pat. No. 5,029,433 to Werk.
The angled hooking cuts are such that the lower band is "woven" or "hooked" onto the upper band to fasten together the overlapping ends in a known manner. The angled hooking cuts can be of any shape to permit the lower band to be "woven" or "hooked" onto the upper band, but generally the cuts comprise an angled cut located between a wide cut region and a narrow cut region on the band. Usually, the bands are relatively biased during the punching action such that once the overlapping ends of the strap are trimmed off, the bands slide somewhat toward each other thereby hooking together the projecting corners of the bands created by the angled hooking cuts in the bands.
Generally the strapping is made from a metal, and in particular steel. It is appreciated that punching and stamping steel in order to effect the desired angled hooking cuts requires a great deal of force. Prior art devices such as those disclosed in U.S. Pat. No. 5,029,433 to Werk and U.S. Pat. No. 4,398,572 to Fromm disclose punching and stamping tools which cause the upper moving die to move in a pivoting or rocking motion. These prior art devices perform this type of pivoting or rocking motion in order to cut a portion of the angled hooking cuts first, cutting the remainder of the angled hooking cuts at a later time thereby reducing the maximum force required to perform the punching procedure.
These prior art devices suffer from several disadvantages. In particular, the rocking or pivoting motion of the die required the housing to be considerably larger than the mounting block upon which the die was mounted. This resulted in an increased amount of dust and dirt entering the housing and increasing the wear of the components. In addition, these prior art devices generally utilized the interaction of a cam on a roller device to create the pivoting or rocking motion. This arrangement resulted in a substantial amount of the forces being transferred through a hairline juncture between the cam and roller device. It is apparent that by having concentrations of such forces on a hairline juncture, increased wear and tear results.